The present invention generally relates to optical processors used in the field of image searching and the like and more particularly to an optical parallel processor for obtaining correlation between image informations.
Conventionally, matched filtering technique is known as a technique for obtaining correlation between an input image and images stored in an optical memory. According to this technique, an optical beam carrying an input image is irradiated on an optical memory device which stores a number of images in a form of Fourier transform hologram. Responsive thereto, a diffraction beam indicating a correlation between the input image and the stored image is produced and the correlation between the images is evaluated by detecting this diffraction beam. In this prior art technique, there is a problem in that the hologram used for storage of information cannot be rewritten as the interference pattern is recorded on a photographic film and the like. Further, the material used for the hologram does not allow superposed recording of a large number of informations.